The present invention relates generally to torque transfer differential systems and more particularly to controllable torque transfer differential mechanisms using magnetorheological fluid.
A differential delivering torque to the wheels of a vehicle allows for wheel slippage and over-spin. Essentially through the gearing within a differential assembly, a balance of torque is achieved for both wheels semi-independent of wheel slippage.
Control of torque and wheel spin in a differential mechanism usually takes the form of friction surfaces and clutch engagement packages. However, one drawback of these systems is that they are usually subject to wear out and fatigue.
Another method used is to use an electrically controllable limited slip differential employing a xe2x80x9cball/rampxe2x80x9d torque multiplier device actuated by a solenoid to provide an electromechanical method to achieve desired friction levels. However, these systems can exhibit nonlinear torque transfer upon actuation.
Another method contemplated is to use magnetorheological (xe2x80x9cMRxe2x80x9d) fluid in a differential mechanism or coupler to control torque transfer. These devices focus on the fluidic shear action of the MR fluid in a disc-to-disc coupling device to transfer torque. One problem with these devices is that the abrasive structure of the MR fluid when actuated causes the friction surfaces to wear out and fatigue.
Linear control of torque transfer is highly desirable in a differential assembly to optimize vehicle performance over traction and stability events.
An object of the present invention is to provide a controllable torque transfer differential mechanism for use in a vehicle.
The above object is accomplished by coupling a closed fluid pump system of magnetorheological fluid to various points on a differential assembly. The pump routes the magnetorheological fluid in a manner for straightforward actuation via a magnetic circuit allowing clear separation of rotating and nonrotating members.
The present invention offers several advantages over previous systems. First, the present invention offers linear control over actuation and corresponding torque transfer. Second, the present invention offers simple differential assembly adaption and a simple electrical actuation method. Third, the present invention requires low power to the actuator. Finally, the present invention offers increased durability over previous MR coupled devices.
Other objects and advantages of the present invention will become apparent upon considering the following detailed description and appended claims, and upon reference to the accompanying drawings.